Scorpius
Scorpius stretches in an S shape above the southern horizon on summer nights. The first thing you'll notice is Antares, a giant star burning red at the scorpion's heart.
| Latin name | Scorpius |
|---|---|
| Abbreviation | Sco |
| Brightest star | Antares (mag ~1.0, variable) |
| Best seen | Summer evenings (Northern Hemisphere) |
| Astrological dates | October 23 – November 21 |
| Sun actually passes | November 24 – November 29 |
| Stars used by Planetica | 1,529 |
How to find it
Scorpius is visible in the evening sky from June to August and is highest in the south around 9 p.m. in July. It sits low in the southern sky, though, so from mid-northern latitudes the tail hugs the horizon. Pick a spot with a wide-open southern view and little light pollution.
The first star to find is Antares. If you see an unusually red 1st-magnitude star low in the southern summer sky, it's almost certainly Antares. Its color is so similar to Mars that the two are sometimes confused; one way to tell them apart is that stars twinkle, while planets twinkle much less.
Up and to the right of Antares (to the west), three stars form a slightly curved vertical line: the scorpion's head. Down and to the left of Antares (to the southeast), a long chain of stars runs on and then curls up sharply like a hook. At its end, the close pair Shaula and Lesath mark the scorpion's stinger. The whole figure looks like the letter S or a fishhook, making it one of the easiest zodiac constellations to recognize. Sagittarius lies to the east, Libra to the west, and Ophiuchus to the north.
The myth: the scorpion that felled Orion
In Greek mythology, Scorpius is the scorpion that brought down the giant hunter Orion. Strong and boastful, Orion bragged that he could hunt every animal on Earth. Offended, a deity (Gaia, goddess of the Earth, or Artemis, goddess of the hunt, depending on the story) sent a small scorpion, which killed Orion with its sting.
Both became constellations, but they were placed on opposite sides of the sky so they would never meet again. Sure enough, Orion, a winter constellation, and Scorpius, a summer one, are never high in the sky at the same time. As Scorpius rises in the east, Orion sets in the west, as if he were still fleeing the scorpion.
Scorpius was an important constellation in East Asia too. Three of the 28 lunar mansions, the Room (房宿), the Heart (心宿) and the Tail (尾宿), lie in Scorpius, and together they form the body of the Azure Dragon that guards the eastern sky. Antares was considered the dragon's heart; in ancient China it was called "Dahuo" (大火), the "Great Fire," and was used to keep track of the seasons.
Main stars
| Name | Apparent magnitude | Distance (approx., ly) | Notes |
|---|---|---|---|
| Antares (Alpha) | ~1.0 (varies slightly) | ~550 | A red supergiant about 700 times the Sun's diameter, with a small companion star. |
| Shaula (Lambda) | 1.6 | ~570 | A hot blue-white star in the scorpion's stinger. |
| Sargas (Theta) | 1.9 | ~300 | A bright, yellowish giant where the tail curves. |
| Larawag (Epsilon) | 2.3 | ~64 | An orange giant in the tail, and the nearest of Scorpius's bright stars. |
Scorpius lies in the Milky Way, so it's packed with things to see. M4, right next to Antares, is about 7,200 light-years away and is one of the closest globular clusters to Earth. M7, near the stinger, is a large open cluster about 1,000 light-years away; it's visible to the naked eye from a dark site, and even the ancient astronomer Ptolemy recorded it. Next to it is M6, the Butterfly Cluster.
Birthday sign dates: two different answers
In astrology, Scorpius (Scorpio) runs from October 23 to November 21. But for most of that period, the real Sun is passing through Libra. Even more surprising, the Sun is actually inside the boundaries of Scorpius only from about November 24 to November 29, a mere 6 days or so. For the next 18 days or so, it passes through Ophiuchus.
The first reason for the difference is precession. Earth's axis wobbles like a spinning top over a cycle of about 26,000 years, moving the vernal equinox point by about 1 degree every 72 years. The astrological signs divide the ecliptic evenly into 30-degree slices from the equinox point, based on the reference of about 2,000 years ago, so they are about a month out of step with the real constellations.
The second reason is the constellation boundaries set by the International Astronomical Union (IAU) in 1930. Most of Scorpius's body lies south of the ecliptic, and the ecliptic crosses only a narrow strip at its northern edge. That's why the Sun spends less time in Scorpius than in any other zodiac constellation. The dates can vary by about a day from year to year.
In Planetica
If your birthday's astrological sign is Scorpio, Planetica places your planetary system next to a real star inside the Scorpius constellation. The candidates are the 1,529 stars in the HYG catalog that lie within about 3,000 light-years of Earth and inside the IAU boundaries of Scorpius. Since this is the direction of the Milky Way, there's a rich mix of stars.
One of them is picked at random, and your system settles about 1–6 light-years from it. "Twin systems" from people with the same name and birthday all sit in Scorpius, but each next to a different star.
Planetica also shows which constellation the Sun was really in on your birthday. For example, someone born on November 10 is a Scorpio in astrology, but on that day the Sun was actually in Libra. Only people born November 24–29 get Scorpius as their real-sky constellation, which makes it quite rare.
Fun facts
- Antares means "rival of Ares (Mars)," a name earned by its Mars-like red color.
- If you put Antares where the Sun is, its surface would extend beyond the orbit of Mars.
- The stars of neighboring Libra were once the scorpion's claws.
Other constellations
Create your own planetary system
Enter a name and a birthday to get a one-of-a-kind planetary system, placed next to a real star in your birthday constellation.